In a chain transmission device for driving a camshaft in which a timing chain is looped over a driving sprocket attached to a crankshaft and a driven sprocket attached to the camshaft, a pivotable chain guide is provided on one side of the slack side of the timing chain, and adjustment force of a chain tensioner is applied to a remote end of the chain guide remote from the center of pivoting movement of the chain guide to tighten the timing chain, so that the chain is prevented from becoming slack and flapping.
Another chain guide is fixed to the tight side of the timing chain, and movements of the timing chain are guided by the fixed chain guide.
One known chain guide for adjusting the tension and for guiding the movement of the timing chain is configured to guide the timing chain by sliding contact with its surface. However, this chain guide has a problem in that the movement resistance of the timing chain is large and a transmission torque loss is significant.
In order to solve this problem, International Publication No. 2010/090139 proposes a chain guide in which both ends of a plurality of roller shafts arranged in a curve form are supported by a guide base elongated in the moving direction of a timing chain, rollers in the form of roller bearings are rotatably supported on the respective roller shafts, and the timing chain is movably supported by the plurality of rollers.
In the above chain guide, since the timing chain is guided while being in rolling contact with the plurality of rollers, movement resistance of the timing chain is small and a transmission torque loss is insignificant.
In the chain guide described in International Publication No. 2010/090139, since the rollers in the form of roller bearings are supported so as not to be movable in the axial direction and the rollers always face the timing chain at the same axial position, radial loads applied to the rollers from the timing chain always act on circumferential portions of the roller shafts from rolling elements of the roller bearings forming the rollers. As a result, the portions where radial loads are applied tend to become worn locally. It is therefore desired to reduce such wear.